The present invention relates generally to air dryers, and more specifically, to a membrane air dryer with sweep air control for a brake system for vehicles.
Air dryers employing membranes consisting of a permeable membrane capable of blocking the passage of nitrogen and oxygen molecules, but allowing water vapor molecules to pass through, as described in U.S. Pat. Nos. 6,719,825 and 5,525,143 amongst many others. In one variation of the technology, the air to be dried passes through the center of the membrane element. The membrane permits the passage of the water vapor to the outside of the membrane, but prevents the passage of the air to the outside of the membrane, thereby drying the air.
To work effectively, the outside of the membrane must be kept dry and at a lower pressure than the inside, creating the partial pressure differential to drive the water vapor out. This is done by providing some fraction of the dry output air as a counter flow sweep air across the outside of the membrane. The sweep air can be provided by sweep air orifice(s) connecting the dry air in the membrane air dryer outlet to the sweep air chamber surrounding the outside of the membrane. The orifices control the volume of sweep air, typically 10-20% of the dryer capacity and create a pressure drop in the sweep air volume. The sweep air and entrapped moisture are expelled to atmosphere.
U.S. Pat. No. 6,719,825 shows a control valve at the inlet for the sweep air. U.S. Pat. No. 5,375,620 shows a self-adjusting flow metering device for the sweep air. An air dryer including a coalescing and charcoal pre-filters and a membrane filter is also shown by U.S. Pat. No. 6,719,825.
The present disclosure is directed to an air dryer, for example, for locomotives, packaged to fit inside a reservoir with a pre-filter exterior the reservoir. The air dryer is generally cylindrical with a circular mounting flange on one end, which bolts to a similar mounting flange welded to the end of the reservoir. This arrangement solves the problem of finding room for the air dryer between main reservoir #1 and #2 on a locomotive, protects the air dryer and especially the vulnerable membrane element from the very high ambient temperatures (as high as 300° F.) during operation of the locomotive in tunnels; protects the air dryer from environmental hazards, like flying stone ballast; eliminates installation piping, and minimizes weight.
The membrane air dryer includes a housing with an air inlet adjacent a first end of the housing, an air outlet adjacent a second end of the housing, a sweep air inlet and a sweep air outlet. A membrane separator has surfaces extending between and connected to the air inlet and the air outlet. A first sweep air passage in the housing extends between the first and second ends of the membrane along and including surfaces of the membrane. The first sweep air passage has an inlet adjacent the air outlet and an outlet adjacent the air inlet and connected to the sweep air outlet. The sweep air inlet and outlet is adjacent the air inlet. A second sweep air passage in the housing extends between the first and second ends of the membrane. The second sweep air passage has an inlet that is connected to the sweep air inlet and is adjacent the air inlet and has an outlet that is adjacent the air outlet and in fluid communication with the inlet of the first sweep air passage.
The first and second sweep air passages are concentric to each other and the membrane. The sweep air from the outlet of the second sweep air passage passes through the membrane to the inlet of the first sweep air passage. A valve is connected between the air inlet and the sweep air inlet and the sweep air outlet is connected to atmosphere.
The membrane air dryer includes a first tube having an first end including an inlet in fluid communication with the outlet of the first sweep passage and an outlet in fluid communication with the sweep air outlet. The first tube has a second end adjacent the air outlet and includes the outlet of the second sweep air passage. The dryer includes a second tube having a first end in fluid communication with the sweep air inlet and having a second end connected to an interior of the first tube between and fluically isolating the inlet of the first tube and the outlet of the second sweep air passage.
A reservoir having an inlet includes the subject membrane air dryer extending from a reservoir inlet into the interior of the reservoir so that the housing air inlet is the inlet of the reservoir, the housing air outlet and the sweep air inlet are interior the reservoir and the sweep air outlet of the housing is exterior the reservoir. A vehicle brake system including a brake controller and the reservoir with the membrane air dryer therein includes a valve connected between the air inlet and the sweep air inlet, and the brake controller controls the valve.
A combination of a reservoir having an air port and a membrane separator having a housing with a separator member between an air inlet and an air outlet and a sweep air inlet and outlet. The housing extends from the reservoir air port into the interior of the reservoir so that the housing's air inlet and sweep air outlet are exterior the reservoir and the housing's air outlet and the sweep air inlet are interior the reservoir. A valve is connected between the air inlet and the sweep air inlet and the sweep air outlet is connected to atmosphere. A vehicle brake system includes a brake controller and the combined reservoir and membrane separator and the brake controller controls the valve.
These and other aspects of the present method will become apparent from the following detailed description of the method, when considered in conjunction with accompanying drawings.